Polyolefin coated fabric reinforcement and cementitious boards reinforced with same

ABSTRACT

The present invention provides a method making glass fiber fabric reinforcements, cement boards, and glass fiber coatings for such reinforcements. The glass fiber fabric reinforcement includes a glass fabric containing multiple yarns containing glass filaments and a polymeric coating disposed onto the multiple yarns to form a coated glass fabric. The polymeric coating comprises a polyolefin based copolymer composition whereby the glass fabric has a Gurley Stiffness measurement of about 100-3000 mg and an ASTM D 638 (2% Secant) modulus of compression of about 1-100 MPa. The reinforcement is sufficiently drapable and lacking in shape memory so as to be curved around the edge of a cement board during the manufacture of same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Division of U.S. application Ser. No. 12/335,937,filed Dec. 16, 2008 now U.S. Pat. No. 7,803,723.

FIELD OF THE INVENTION

This invention relates to coated reinforcing fabrics, and moreparticularly to drapable fabric reinforcements for cementitiousmaterials.

BACKGROUND OF THE INVENTION

Cementitious boards useful in the construction industry are known tocontain inorganic, hydraulically setting material, such as Portlandcement or gypsum. Hydraulic gypsum and cement, once set, have verylittle tensile strength and are usually reinforced with facing materialswhich improve the resistance to tensile and flexural loads. This hasbeen the basis for using paper facing on conventional gypsum wall boardand non-woven glass fiber scrim in cement boards.

Glass fiber meshes have been popular as a facing sheet in cement boardsbecause they can increase the dimensional stability in the presence ofmoisture and provide greater physical and mechanical properties.However, most glass fiber compositions, other than AR glass, degrade inthe alkali environment of a cement core, so they must be coated with aprotective finish.

Cementitious boards have been manufactured by casting a hydraulic cementmixture in the form of a thin, indefinitely long panel. See U.S. Pat.No. 4,504,335, which is hereby incorporated by reference. The hydrauliccement is usually a mortar containing a mixture of water and Portlandcement, sand, mineral or non-mineral aggregate, fly ash, accelerators,plasticizers, foaming agents and/or other additives. The mortar slurryis deposited onto a glass reinforcing network having a strippable papersheet thereon, which is fed from a roll to pass over a forming table andunder a continuous stream of mortar. The mortar is then distributedacross the breadth of the carrier sheet, and the mortar-laden carriersheet is towed through a slit defined by a supporting surface and acylindrical mortar screeding roller mounted above the supporting surfaceso that its axis is transversely parallel to the supporting surface. Thelong network of reinforcing fibers is drawn against the roller andthrough the slit, rotating the roller counter to the direction of thetravel of the carrier sheet, whereby the roller presses the network intothe surface of the mortar and wipes mortar adhering to the roller intothe interstices of the network. The network then tows the resultingbroad, flat ribbon of mortar towards a cutter.

Similarly, British Patent Specification No. 772,581 teaches a productionof reinforced plasterboard by a method which comprises spreading plasteron a first conveyor belt, dumping the plaster onto a plaster-soakedreinforcing mesh which is being transported by a second conveyor belt,and passing the plaster under a pressure roller to produce a ribbon ofthe required thickness. A second plaster-soaked mesh is dragged onto theupper surface of the ribbon as the mesh is fed under a third conveyorbelt mounted above and in pressing relationship to the ribbon ofplaster.

In still another process, as described in Lehnert et al., U.S. Pat. No.4,647,496, a randomly oriented fibrous glass mat is fed onto acontinuously moving belt onto which gypsum slurry is poured. The topsurface of the gypsum ribbon thus formed is layered with a secondrandomly oriented glass mat which forms a sandwich with the gypsum coreand the lower glass mat.

Other fiber and coating technologies possibly useful in fabricreinforcements include those found in U.S. Pat. Appl. 2006/0188719 (nowU.S. Pat. No. 7,045,209); U.S. Pat. Nos. 4,532,275 and 3,600,269; andBeren, J. R.; Heterophasic polypropylene copolymer resins for extrusioncoating, Polymer, Laminations and Coatings Conference 1994, pp 102-112(1994); Marques, M. V; Poloponsky, M; Chaves, G. E; Influence of theelastomeric polypropylene addition on the properties of commercialmetallocenic polypropylene, Mat. Res., 4,4, (2001); and Mascia, L;Dhillon, J; Harper, M. F; Adhesions Enhancement of rubbery and ductilepolyolefin coatings on glass fibers for epoxy composites and effects onfailure mechanism, Journal of Applied Polymer Science, 47, 3, pp487-498, (1993), which are hereby incorporated herein by reference intheir entirety.

Woven knit and laid scrim fabrics used in cementitious boards may becoated either:

(a) before fabric-forming, as in single-end-coated fabrics;

(b) in-line (normally roller or dip coated) concurrently with formationsuch as in the case of laid scrim non-woven meshes; or

(c) off-line coated after formation (normally roller or dip coated),typically used with many woven fabrics. In the case of coating beforefabric-forming, the cost of coating each strand individually, in anoperation prior to weaving, may be prohibitive. In the cases of in-lineor off-line coating operations, the coating levels of the machinedirection (“MD”) and cross-machine direction (“CD”) yarns are generallynot independent.

Unequal coating levels between the MD and CD yarns, normally found indip coated fabrics, results in an “imbalanced coating weightdistribution ratio” in which more coating is deposited on the lowtension CD yarns than on the relatively higher tension MD yarns. This“imbalance” often leads to undesirable properties of reinforcementsespecially those which have been treated or coated for corrosion or fireresistance. In corrosive environments, such as cement-based matrices,heavier coating in the CD implies lower, possible inadequate coatingprotection on the MD. Both quantity and quality of coating in the MDsuffers. The tensioned, twisted MD bundle does not allow coating topenetrate within the bundle. As a result substantial pockets of airremain in the MD bundle. The poor quantity and quality of coating on theMD strands leads to poor corrosion protection of the MD strands relativeto that of the CD strands, especially in an alkali environment likecement.

A balanced coating weight distribution is desirable. It is easy toachieve in the case of single-end-coated (SEC) fabrics as each strand isindependently and explicitly coated with a given level of coating. Thecoated strands are then combined into a fabric with the ratio of coatingweight (DPU_(cd)/DPU_(md)) being established simply by selection ofyarns containing the desired coating weights-often selected to be thesame in MD and CD.

Current glass scrim reinforcements typically include a coating of PVCplastisol, a blend of PVC particles dispersed in plasticizer (usuallyphthalate based). By necessity, such coatings contain heat stabilizersand varsol (or other paraffin oil based solvent) to control viscosity.Despite the presence of the heat stabilizer, it is not advisable to dryPVC at too high a temperature or it will de-polymerize. The phthalateplasticizer has also come under increased scrutiny for its VOCemissions. The solvent used to control viscosity also tends to evaporateduring drawings and yields voids in the coating, leading to decreasedalkali resistance in certain locations such that cement, being alkaline,will dissolve uncoated glass fiber surfaces.

The manufacturing plant will also need to burn off the solvent with anoxidizer. Since the plasticizer has some affinity for the PVC particlesdispersed in it, it becomes more viscous over time as the plasticizermigrates into the PVC. This problem is exacerbated in the summer monthswhen the manufacturing plant is much warmer. A plant chemist is requiredto adjust viscosity to compensate for evaporation using additionalsolvent. This can lead to some variability in coating quality andthickness. Often, batches of plastisol are lost when the viscosity goestoo high. In the dip process, where an entire fabric is immersed in theplastisol while it is on the tenter frame, there is much more tension inthe yarns in the machine direction than the yarns in the cross machinedirection, so much more plastisol is picked in the cross machinedirection yarns during coating, resulting in an imbalanced coating. Thisnecessitates using an unnecessarily large amount of plastisol on thescrim so that the machine direction yarns are properly coated to get thesame performance as the cross machine direction yarns.

Accordingly, there remains a need for woven, knit or mesh-type non-woven(“scrim”) fabrics which have a uniform coating of an alkali-resistantmaterial which is easily applied, and which generates less VOCs, butwhich is also drapable and strong, as well as methods for producing suchcoating on yarn for improving manufactured properties of cement boards,for example, and for protecting these fabrics in environments whichrequire corrosion and flame resistance, for example.

SUMMARY OF THE INVENTION

In accordance with a first preferred embodiment of the presentinvention, a glass fiber fabric reinforcement is provided which includesa glass fabric containing multiple yarns containing glass filaments anda polymeric coating disposed onto the multiple yarns to form a coatedglass fabric. The polymeric coating includes a polyolefin (such as apolypropylene or a polyethylene-based co-polymer composition). Thecoated glass fabric results in a Gurley Stiffness measurement of about100-3000 mg and an ASTM D 638 (2% Secant) modulus of compression ofabout 1-100 MPa, the reinforcement being sufficiently drapable andsufficiently lacking in shape memory so as to be curved around the edgeof a product to be reinforced, such as a polymer matrix, gypsum board,or cement board, during the manufacture of same.

The polyolefin-based compositions of this invention are much more heatstable than conventional PVC plastisol coatings so that they will notde-polymerize during exposure to heat. These polyolefin coatings areparticularly advantageous for extruding filaments and yarns made of highstrength material such as glass. The extrusion of polypropylene andpolyethylene, in particular, avoids many of the negative issuesassociated with plasticizer, since the coating will always have the sameviscosity and rheology at the same temperature. Predictably, thereshould be no voids in the polyolefin coatings of this invention, nosolvent to be removed, a relatively uniform coating, and very littlechance of having to scrap a batch of coating because the viscosity ofthe batch is not optimized. Furthermore, polyolefin extrusion coatingsdo not require phthalate plasticizer for flexibility, and do not requirethe use of stainless steel coated extruder parts, which are necessary inthe making of PVC plasticizer, as HCl gas is given off in the process.

In further embodiments of the present invention, the polyolefin basedpolymer or copolymer composition is extruded, or otherwisesingle-end-coated (SEC), over individual yarns intended to be used inthe resulting reinforcement fabric. Ideal polypropylene copolymercompositions include a heterophasic copolymer of polypropylene, or ablended mixture of polypropylene homopolymer and ethylene-propylenerubber.

In still a further embodiment of the present invention, a glass fibercoating composition is provided which comprises about 70-80 wt. %heterophasic polypropylene copolymer; about 10-30 wt. % polypropylenehomopolymer; about 1-5 wt. % ethylene-olefin copolymer; about 2-4 wt. %maleic anhydride-g-polypropylene; about 0-20 wt. % inorganic filler andabout 500-1500 ppm vinylidene fluoride-hexafluoroalkene copolymer.

The process used for coating PVC plastisol for glass scrims is to dipcoat the scrim and dry the coating, which is relatively limiting from aproduction standpoint. The polyolefin coatings of the present inventionare derived from a polymer melt using a preferred extrusion technologyand hence, can be run at much higher line speeds. Polymer melts may havesmall traces of low molecular weight fractions; “solventless” orextremely low “VOC emissions” would also be appropriate. While one wouldthink that one could replace dip-coating applications of PVC plastisolby extrusion coating directly onto glass yarns, plasticized PVC migratesout of the coating when aged at elevated temperatures, such as thecuring temperature for cement board, thus making the thin extrudedcoating very brittle and vulnerable to cracking. The present inventionemploys little or no plasticizer or low molecular weight additives, suchas mineral oils or solvents, in preparing its “soft” polyolefincopolymer compounds. The present invention also takes advantage ofcompatible sizes for polypropylene, which have been developed forpolypropylene reinforced composites.

In a further embodiment of the present invention, a cement board isprovided which includes a cement matrix and a glass fabric containingglass filaments. At least the yarns and the glass fabric are coated witha polymeric coating composition comprising a polyolefin compositionresulting in a Gurley Stiffness measurement of about 100-3000 mg and anASTM D 638 (2% Secant) modulus of compression of about 1-100 MPa. Thecoated glass fabric is embedded into at least one surface of thesomewhat viscous cement board, such that the glass fabric issufficiently drapable so as to be curved around an edge of the productto be reinforced, during the manufacturing of same, withoutsignificantly springing back into its original form. The polymericcoating is desirably applied in a thickness of about 0.04-1.0 mm,preferably about 0.4-0.7 mm, and most preferably about 0.5-0.55 mm.

A BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described with reference to thefollowing drawings:

FIG. 1 is a side cross-sectional view of a cement board of the presentinvention showing an embedded fabric;

FIG. 2 is a diagrammatic side cross-sectional view of a yarn beingextruded with the preferred polyolefin compositions of this invention;

FIG. 3 is an enlarged cross-sectional view of the coated yarn takenthrough line 3-3 of FIG. 2, showing glass filaments in a yarn with anapplied coating;

FIG. 4 is a step by step flow diagram of a preferred method of making acement board according to this invention;

FIG. 5 is a diagrammatic, side elevation view of a proposed continuousmanufacturing line for producing cementitious boards using the fabric ofthis invention; and

FIG. 6 is a graphical depiction of Gurley Stiffness (mg) of coatedscrims showing polymer composition vs. Gurley Stiffness (mg).

DEFINED TERMS

In accordance with the present invention, the following definitions areused:

Areal weight. The weight of coated or uncoated fabric per unit area(width×length).

Cementitious material. An inorganic hydraulically setting material, suchas those containing one or more of: Portland cement, mortar, plaster,gypsum, and/or other ingredients, such as, foaming agents, aggregate,glass fibers, moisture repellants and moisture resistant additives andfire retardants.

Composite facing material. Two or more layers of the same or differentmaterials including two or more layers of fabrics, cloth, knits, mats,wovens, non-wovens and/or scrims, for example.

Fabric. Woven or non-woven flexible materials, such as tissues, cloth,knits, weaves, carded tissue, spun-bonded, point-bonded, and mesh-typescrim wovens and non-wovens, needled or braided materials.

Fiber. A general term used to refer to filamentary materials. Often,fiber is used synonymously with filament. It is generally accepted thata filament routinely has a finite length that is at least 100 times itsdiameter. In most cases, it is prepared by drawing from a molten bath,spinning, or by deposition on a substrate.

Filament. The smallest unit of a fibrous material. The basic unitsformed during drawing and spinning, which are gathered into strands offiber for use in composites. Filaments usually are of extreme length andvery small diameter. Some textile filaments can function as a yarn whenthey are of sufficient strength and flexibility.

Glass. An inorganic product of fusion that has cooled to a rigidcondition without crystallizing. Glass is typically hard and relativelybrittle, and has a conchoidal fracture.

Glass fiber. A fiber spun from an inorganic product of fusion that hascooled to a rigid condition without crystallizing.

Knitted fabrics. Fabrics produced by interlooping chains of filaments,roving or yarn.

Mat. A fibrous material consisting of randomly oriented choppedfilaments, short fibers, or swirled continuous filaments held togetherwith a binder.

Roving. A number of yarns, strands, tows, or ends collected into aparallel bundle with little or no twist.

Scrim. A low cost reinforcing fabric made from continuous filament yarnor strand in an open-mesh construction; can be woven or laid, forexample.

Sizing. A substance or process of applying the substance directly onfibers of a fabric or yarn for strengthening, imparting chemicalcompatibility to, or protecting, the fibers of a fabric or a yarn.

Strand, One or more fibers or filaments in a group that is handled as anentity as an input in a textile process, e.g., a twisted roving or yarn.

Tensile strength. The maximum load or force per unit cross-sectionalarea, within the gage length, of the specimen. The pulling stressrequired to break a given specimen. (See ASTM D579 and D3039)

Tex. Linear density (or gauge) of a fiber expressed in grams per 1000meters.

Textile fibers. Fibers or filaments that can be processed into yarn ormade into a fabric by interlacing in a variety of methods, includingweaving, knitting and braiding.

Warp. The yarn, fiber or roving running lengthwise in a woven, knit orlaid or woven scrim fabric. A group of yarns, fibers or roving in longlengths and approximately parallel.

Weave. The particular manner in which a fabric is formed by interlacingyarns, fibers or roving. Usually assigned a style number.

Weft. The transverse threads or fibers in a woven, knit or laid or wovenscrim fabric. Those fibers running perpendicular to the warp. Alsocalled fill, filling, yarn or woof.

Woven fabric. A material (usually a planar structure) constructed byinterlacing yarns, fibers, roving or filaments, to form such fabricpatterns as plain, harness satin, or leno weaves, for example.

Woven roving. A heavy glass fiber fabric made by weaving roving or yarnbundles.

Yarn. An assemblage of twisted filaments, fibers, or strands, eithernatural or manufactured, to form a continuous length that is suitablefor use in weaving or interweaving into textile materials.

Zero-twist-yarn. A lightweight roving, i.e., a strand of near zero twistwith linear densities and filament diameters typical of fiberglass yarn(but substantially without twist).

DETAILED DESCRIPTION OF THE INVENTION

Facing materials, cementitious boards and methods of manufacturingcementitious boards having the facing materials of this invention areprovided. Facing materials which are embedded totally, or onlypartially, so as to present a fibrous facing, are within the scope ofthis invention. The fabric reinforcements of this invention can beemployed in many end-use reinforcement applications, such as, forexample, gypsum and cement boards, asphalt and road reinforcement,roofing applications, soil reinforcement, polymer-matrix reinforcement,and as stand-alone coated fabrics in filters, screens and garmentapplications.

With reference to the Figures, and particularly to FIGS. 1-6 thereof,there is depicted a cement board 100 and coated glass fabricreinforcement 10 having coated warp yarns 16 and coated weft yarns 14disposed in a preferred laid scrim, useful as an embedded facing layerof the preferred cement board 100 of this invention. Needled, woven,knitted, braided and mesh-type non-woven and composite materials can beemployed because of their impressive strength-to-weight ratio and, inthe case of wovens, braided, knits, and non-woven mesh-types (alsoreferred to as “scrim”), their ability to form weft and warp yarnpatterns which can be manipulated to create directional absorption ofcoatings, or even intentionally “unbalanced” coating weightdistributions. While the facing layers of this invention can containfibers and filaments of organic and inorganic materials, the mostpreferred fibers contain glass (AR, E, C, ECR, R or S-glass), olefin(such as polyethylene, polystyrene and polypropylene), Kevlar®,graphite, rayon, polyester, carbon, ceramic fibers, mineral fibers, orcombinations thereof, such as glass-polyester blends or Twintex®glass-olefin composite, available from St. Gobain Corporation, France.Of these types of fibers and filaments, glass compositions are the mostdesirable for their fire resistance, low cost and high mechanicalstrength properties. The most preferred yarns are olefin coated C or Eglass.

In a first embodiment of the present invention shown in FIG. 1, a cementboard 100 is provided, including a cement matrix 101 and coated glassfabric reinforcement 10, which, preferably, presents a thin cementitiouslayer 108 on its surface. The coated glass fabric reinforcement 10includes, preferably, individually coated warp yarns 16 and weft yarns14 in a laid scrim. The cementitious core 101 can further includeperformance additives 12 which can be added to the slurry precursor ofthe core 101. Cement boards having cementitious surfaces and a mesh ofreinforcing fibers underlying the top, bottom and longitudinal edgesurfaces are presently known, see, for example, U.S. Pat. No. 4,916,004,which discloses the use of a woven glass fiber mesh embedded into acement matrix.

The preferred glass mat reinforcement 10 of the present inventionincludes polyolefin based coatings. The invention particularly employs“soft” polyolefin compositions which have a Gurley Stiffness measurementof about 100-3000 mg and an ASTM D 638 (2% Secant) modulus ofcompression of about 1-100 MPa, when coated onto glass yarns. The glassfiber fabric reinforcement 10 of this invention is, desirably,sufficiently drapable so as to be folded around the corners of thecement board before final setting. Folding can be accomplished by acombination of guide flanges and rollers which thus embed the fabricreinforcement 10 near the upper surface of the board 100 along with apreferred separate top fabric reinforcement 25 to form overlappingportions along the lateral sides, as shown in FIG. 1. The embedding ofthe fabric reinforcement 10 must, of course, take place before theinitial set of the concrete has occurred, but the mix should not be sosoupy at the point of embedding that the mesh will rise up again afterpassing under a forming spatula or guide. The Gurley Stiffness of thefabric desirably is similar to conventional PVC plastisol coated glassfabric so as to, preferably, permit the use of the fabrics of thisinvention in conjunction with existing continuous cement and gypsumboard manufacturing equipment with little or minor adjustment.

As shown in FIGS. 2 and 3, the preferred coated warp yarn 16 and coatedweft yarn 14 are individually manufactured by drawing a glass fiber yarnor roving 115 through an extrusion die 200, whereby a polymeric coating107 is applied uniformly to the yarn or roving 115. As shown in FIG. 3,the coating 107 is relatively uniform about the yarn and coats at leastthe exterior side of the outlying filaments 220, but, depending on theviscosity and temperature of the polymeric coating, some or totalimpregnation within the openings of the yarn or roving 115 can beaccommodated.

As disclosed in FIG. 4, the present invention includes the steps ofcoating the individual yarns 110, primarily by extrusion, although dipcoating can be less desirably employed in some circumstances. The coatedindividual yarns are then formed into a coated fabric at step 120. Thefabric can be woven or non-woven, although laid scrim whereby the weftyarns are alternated above and below the warp yarns is preferred. Thecoated fabric is then transported at step 130 to a preferred continuouscementitious board line. The coated fabric is then contacted andembedded into a cementitious core material at step 140, followed bypermitting the cementitious material to set at step 150. During thesetting of the cementitious material, the slurry solidifies and reachesan elevated temperature. The polyolefin compositions used to form thecoated fabric of the present invention would most desirably, but notnecessarily, have a higher melting temperature than the temperature atwhich the cementitious material sets, so as to provide a homogenous andcontinuous coating for protecting against corrosion resistance in analkaline environment after the cementitious material is hardened.Following setting of the cementitious material step 150, the board istrimmed at step 160, such as by mechanical saw or water knife. Furtherdetails of the manufacturing process are explained below.

Fabric Fabrication Process

Once the continuous glass fibers have been produced they must beconverted into a suitable form for their intended application. The majorfinished forms are continuous roving, woven roving, fiberglass mat,chopped strand, and yarns for textile applications.

The fabric reinforcement 10 of the invention can be made in manyconstructions, such as laid scrim, stitchbonding or warp knitting, andcan be made by conventional means such as plain weaving, twill or satinweaving, unidirectional weaving, knitting or stitchbonding. Fine-fiberstrands of yarn from the forming operation can be air dried on formingtubes to provide sufficient integrity to undergo a twisting operation.Twist provides additional integrity to yarn before it is subjected tothe weaving process, a typical twist consisting of up to 0.7-1.0turns/inch. In many instances heavier yarns are needed for the weavingoperation. This is normally accomplished by twisting together two ormore single strands, followed by a plying operation. Plying essentiallyinvolves retwisting the twisted strands in the opposite direction fromthe original twist. The two types of twist normally used are known as Sand Z, which indicate the direction in which the twisting is done.Usually, two or more strands twisted together with an S twist are pliedwith a Z twist in order to give a balanced yarn. Thus, the yarnproperties, such as strength, bundle diameter, and yield, can bemanipulated by the twisting and plying operations. Fiberglass yarns areconverted to fabric form by conventional weaving operations. Looms ofvarious kinds are used in the industry, but the air jet loom is the mostpopular.

Zero twist-yarns may also be used. This input can offer the ease ofspreading of (twistless) roving with the coverage of fine-filamentyarns. The number of filaments per strand used directly affects theporosity and is related to yarn weight as follows: n=(490×Tex)/d², where“d” is the individual filament diameter expressed in microns. Thus, ifthe roving with coarse filaments can be replaced with near zero twistyarn with filaments half the diameter, then the number of filamentsincreases by a factor of 4 at the same strand Tex.

The major characteristics of the knit or woven facing embodiments ofthis invention include its style or weave pattern, fabric count, and theconstruction of warp yarn and fill yarn. Together, these characteristicsdetermine fabric properties such as drapability and performance in thefinal board. The fabric count identifies the number of warp and fillyarns per inch. Warp yarns run parallel to the machine direction, andfill yarns are perpendicular.

When the preferred glass fibers are employed, a sizing is generallyused. Preferred sizings for use with a fibrous layer comprised of glassfilaments include aqueous sizings comprising one of the followingblends: 1) an epoxy polymer, vinyl and amine coupling agents and anon-ionic surfactant; 2) an epoxy polymer, amine coupling agent and anon-ionic surfactant; 3) an epoxy polymer, methacrylic and epoxycoupling agents, and cationic and non-ionic surfactants (paraffinlubricants); 4) anhydrous polymerized acrylate amine (for example, thesubstance disclosed in PCT Patent Application No. WO 99/31025, which isincorporated herein by reference), methacrylic and epoxy coupling agentsand a non-ionic surfactant; and 5) anhydrous polymerized epoxy amine(for example, as disclosed in U.S. Pat. No. 5,961,684 to Moireau et al.,which is incorporated herein by reference), vinyl and amine couplingagents, and a non-ionic surfactant, each of the above blends beingproduced by Cem FIL Reinforcements of Saint Gobain Vetrotex Cern-FIL®S.L., a Saint Gobain Vetrotex company. Preferably, the non-ionicsurfactant comprises an organo-silane. These sizings are compatible withthe preferred coatings for the preferred fabric reinforcement 10 and thecementitious core 101, and improve initial fiber strength and ease offabric forming. The sizings preferably comprise not more than 2.5% byweight, and most preferably less than 1.5% by weight of the fibrouslayer. The preferred sizing is one that is compatible with polypropylene(PP), such as those conventionally used for PP composites. See U.S. Pat.No. 5,648,169, for example, which is hereby incorporated by reference inits entirety.

The following fabric styles and categories are useful in the practice ofthis invention:

Fabric Areal wt. grams/m2 Areal wt. oz/yd2 Light weight 10-35  3-10Intermediate weight 35-70 10-20 Heavy weight  59-300 15-90

Fabric Thickness μm Thickness mil Light weight  25-125 1-5 Intermediateweight 125-250  5-10 Heavy weight 250-500 250-500

It has been determined that the fabric reinforcement 10 desirably has anareal weight of about 15-300 grams/m², preferably about 30-150 grams/m²,and thicknesses of about 5-22 mils, with 10-15 mils being mostpreferred. The linear density of the preferred glass fibers preferablyranges from about 50 tex where yarns are employed, to 2,500 tex whererovings are employed, with 68 tex being currently preferred. Wherecarbon fibers are used, they're preferably provided as tows, with thefilament count preferably ranging from about 3,000 to 24,000. Preferredproperties of glass fibers include a virgin filament tensile strength ofat least about 185,000 psi or higher; Young's modulus of elasticity ofabout 10-12 million psi; strain at breaking point of at least about 1.5%or higher; water uptake at less than about 0.1%, and softeningtemperature of about 860° C. The preferred fabric reinforcement 10should also possess an ASTM D309 tensile strength of at least about 20psi in the machine direction and about 5 psi in the cross-machinedirection.

In certain applications, exposed (projecting out of the non-woven, scrimor woven fabric) but coated fibers are acceptable to enable attachment.In cement boards generally, each yarn or coating should be as completelycoated as possible to avoid corrosion. Some exposed coated fibers enableattachment to factory or field applied coatings or adhesives such asPortland cement based mortar, acrylic adhesive, silicone adhesive andglue on the outer surface of the cementitious board. The selectedbinders and finishes should also minimize “blocking” (adhesive bondingbetween adjacent boards during storage). Additionally, the preferredbinders can be provided with additives, such as UV and mold inhibitors,fire retardants, etc. Carboxylated polymer additions to the binder resincan promote greater affinity to set gypsum, or to Portland cement-basedmortars, for example, but are less subjected to blocking than resinswithout such additions.

The binders or finishes can be applied in 1, 2 or 3 layers or passes.The first application quality depends highly on tensions and twistlevel. If, after this coating is fused, a second coating (binder orfinish) is applied, the tension and twist is a little less important asthe strands are now acting as if they were monofilament yarns becausethey have a monolithic coating on them. Additional coatings areoptional, and without them, the resulting porosity is generally veryhigh. This is good as the reinforcement is generally buried just beneaththe surface of the cement board. High porosity aids in this embedding.Subsequent coatings to reduce porosity may not be necessary except inthe case where a very smooth surface is required.

The fabrics reinforcements 10 of this invention can be further coatedprior to adhering these layers to a core 101 in order to further reduceporosity, to resist slurry penetration, reduce corrosion, improvestrength or fire resistance, and/or to reduce the “fuzziness” of thesurface, which can lead to some itching during repeated handling. Theadditional coating is distinguished from the sizing or binder used tobond the fibers together to form the individual layers, as describedabove, but can be the same or different composition. The additionalcoating can include those described in U.S. Pat. No. 4,640,864, which ishereby incorporated by reference, and are preferably water-resistantand/or fire-retardant in nature. They are preferably applied during themanufacture of the fabric reinforcement 10 of this invention, but may beapplied by the board manufacturer prior to use in making cementitiousboards 100.

The additional coating 107 applied to the fabric reinforcement 10, asshown in FIG. 3 of this invention, preferably coats the glass strands220 in the warp yarns 16 and weft yarns 14 of the fabric reinforcement10. Alternatively, the additional coating 107 can increase or decreasethe wetting angle of the cementitious slurry to reduce penetration orincrease adhesion. The coating 107 can further contain a UV stabilizer,mold retardant, alkali-resistant formulation, water repellant, a flameretardant and/or other optional ingredients, such as dispersants,catalysts, fillers and the like. The coating 107 can be in melt orliquid form and the fabric reinforcement 10 is led through the melt orliquid, or the melt or liquid is sprayed (with or without a water sprayprecursor) on one or both sides of the fabric reinforcement 10.

The preferred additional coating of this invention can contain aresinous mixture containing one or more resins. The resin can containsolid particles or fibers which coalesce or melt to form a continuous orsemi-continuous coating over and through the yarns. The coating 107 canbe applied in various thicknesses to sufficiently cover the fibrousconstituents of the fabric reinforcement 10 so that no fibers protrudefrom the added coating, or to such a degree that the fibers protrudefrom the added coating so that they can be used to join to additionallayers in a EIF system or to mortar for tile, for example. Theadditional coating can form an alkali barrier which protects the fabricfrom alkaline cement cores, for example. The additional coating cancomprise a thermoplastic or a thermoset resin, although extrudedpolyolefin copolymers are preferred.

The coating 107 can be formed from a mixture of resin and fillers, suchas silicates, silica, gypsum, titanium dioxide and calcium carbonate. Inaddition, fire retardants, such as bromated phosphorous complex,halogenated paraffin, colloidal antimony pentoxide, borax, unexpandedvermiculite, clay, colloidal silica and colloidal aluminum can be addedto the resinous coating 107 or saturant. Furthermore, water resistantadditives can be added, such as paraffin, and combinations of paraffinand ammonium salt, fluorochemicals designed to impart alcohol and waterrepellency, such as FC-824 from 3M Co., organohydrogenpolysiloxanes,silicone oil, wax-asphalt emulsions and poly(vinyl alcohol) with orwithout a minor amount a minor amount of poly(vinyl acetate). The addedcoating can include pigment, such as kaolin clay, or lamp blackthickeners such as modified bentonite clay, defoamers, such as fattyacid/polyglycol mixtures, UV resistance additives, setting accelerators,such as clay compounds, polyacrylamide, potassium salts, or combinationsthereof, and dispersants such as sodium polyacrylate. Knownpreservatives and, of course, water can be added in latex compositions,and solvents in thermosetting compositions. (See, for example, U.S. Pat.No. 4,640,864, which includes insulation boards includingpolyvinylchloride based coatings including fire- and water-repellants,and which is hereby incorporated by reference). Other additives,suggested herein as being useful in the binder or cementitious core 101,could also be employed in the added coating.

The resinous coating 107 as shown in FIG. 3, is preferred where thefibrous layer is comprised of non-AR glass; however, coatings are notnecessary where the fibrous layer is comprised of AR-glass, PVA, carbonor aramid fibers. The resinous coating 107 desirably provides mechanicaland chemical protection to the glass filaments or strands 220. Theresinous coating 107 is preferably a polyolefin such as polyethylene(“PE”) or polypropylene (“PP”), which has been made “soft” so as to makethe resulting fabric reinforcement 10 drapable and less resilient.

Customers who manufacture cement boards 100 expect the “hand feel” and“drapability” of the glass reinforcement to be similar to current PVCplastisol coated product. From a practical standpoint, this means thefabric reinforcement will preferably play off the roll in a similarfashion to the current PVC plastisol product, and will preferably have asimilar drapability and lack of shape memory when the reinforcement iscurved around the edge of the cement board, as shown in FIG. 1.

The polyolefin coating compositions of this invention preferably have aGurley Stiffness measurement of less than 5000 mg, more preferably about100-3000 mg, and most preferably about 500-2500 mg. Gurley Stiffness isa technique used to determine the bending moment of fabrics, scrims andother similar materials. The technique provides information on thedrapability of fabric. Scrim with very high Gurley Stiffness values,such as those over 5000 mg, would be too stiff to be wound around thespools, and any coating on the scrim would likely crack. Additionally,fabric and scrims as a reinforcement in cement board compositeapplications should be flexible so as to provide better impact toughnessduring bending. At the lower end of the range, the Gurley Stiffnessshould be at least 100 mg, and most preferably, about the same stiffnessas a PVC plastisol coated scrim, which is currently the benchmark forflexibility. The fabric reinforcement 10 should also have an ASTM D 638(2% Secant) modulus of compression of about 1-100 MPa, and morepreferably about 5-35 MPa.

Polypropylene resin can be extruded over individual yarns and filamentswithout the use of a plasticizer. The polypropylene coating willgenerally have the same viscosity and rheology at the same temperature,and there are hardly ever voids in the coating, or solids to be removed.Extrusions of polypropylene and polyethylene provide a uniform coating,and rarely does a batch of coating material need to be scrapped for notmeeting viscosity requirements. This invention creates “soft” versionsof polyolefin compositions because relatively pure polypropylene andpolyethylene coated yarns would not be very drapable and would result ina stiff fabric that would be difficult to bend around corners. Thedesired fabric should be soft enough to form about a 0.5 in radius in oron a cement board 100 without springing back to its original shape priorto initial setting. Polypropylene emulsions, while technically feasible,are not a very good option for coating reinforcements for cement boards,since such emulsions are typically waxes, and become too brittle forcement board reinforcement applications.

Applicants' extrusion coating with polyolefin compounds over glass yarnsis an improved technology platform. Quantity polyolefins such aspolyethylene and polypropylene would be inexpensive alternatives to PVCplastisols. Polymers like acrylics could be used but are relatively moreexpensive. Polypropylene compounds are most desirable, since sizing hasbeen developed for polypropylene reinforced composites for some time,and could be adapted for glass yarns.

The present invention, therefore, relies principally upon polypropyleneextrusion coating of glass yarns as a proposed alternative to PVCplastisol or plasticized PVC coated glass yarns. The compositionsgenerally comprise a blend of a major portion of a first polymericcomponent, which is either reactor made, heterophasic copolymer of PP orpost-reactor blended mixtures of PP homopolymer and ethylene-propylenerubber. Other PP or PE compositions are also satisfactory. The reactormade heterophasic copolymers are slightly more desirable due toincorporation of high ethylene content. A second minor component of lowdensity ethylene-α-olefin polymer can be added to improve melt flow. Thecomposition, additionally, can include maleic anhydride modified PP asan adhesion promoter, and may also additionally include inorganicfillers such as talc or vinylidene fluoride-hexafluropropylenecopolymer. The glass fiber laid scrims prepared from the preferredextrusion processes coat glass yarns individually in the polyolefincomposition, preferably including a polypropylene copolymer as a majorcomponent, and up to 5 wt % ethylene-olefin copolymer. Some “soft” PPcompositions, compared to stiffer resinous compositions, are describedbelow.

TABLE 1 Stiffness values of compression molded films and glass scrimscoated with different formulations based on PP. Gurley ASTM D 638Stiffness (2% Secant of scrims Formulation Type Modulus) (mg) PVCplastisol ~17 MPa ~1350 (1X) PP homopolymer ~900-1000 Mpa ~8000 (6X) PPhomopolymer + ethylene-α-olefin ~400-700 Mpa ~5000 (4X) PP copolymer +PP homopolymer + ~19-25 Mpa ~1600 ethylene-α-olefin PP copolymer +ethylene-α-olefin + PP ~30 Mpa ~1750 homopolymer + talc

TABLE 2 Preferred “Soft” PP formulations. Composition Type wt % or ppmFunction Heterophasic PP copolymer 70-80 Flexibility PP homopolymer10-30 Improve processability Ethylene-olefin copolymer 0-5Processability, softness Maleic anhydride-g-PP 2-4 Adhesion promoterTalc (treated or untreated) 0-20 Filler, adhesion inorganic filler tocement Vinylidene fluoride- 500-1500 ppm Process aid, reducehexafluoroalkene copolymer surface roughness, higher line speeds

As can be shown in FIG. 6, the Gurley Stiffness is greatly enhanced byPP copolymer compounds of this invention, with the polypropylenecopolymer and polypropylene homopolymer blends, includingethylene-α-olefin performing most similarly to the PVC plastisolconventional reinforcement.

HECO Resins

Polymer blends are now regarded as an economical alternative to thedevelopment of new polymers. Marques et al., at p. 1. Materials withimproved end use properties can be obtained by blending polymers withdifferent molecular characteristics. Id. In the case of polyolefins,they are immiscible since small differences in the shape of themolecules give rise to unfavorable intermolecular forces. Id. Furtherimmiscibility arises as the polyolefins crystallize into differentcrystal domains. Id.

While having a number of valuable properties and economic benefits,polypropylene homopolymer exhibits a poor impact resistance, mainly atlow temperatures. Id. This fact is due to its relatively high glasstransition temperature (Tg). Id.

The improvement of some of these properties is typically achieved byblending polypropylene to other polymers or with reinforcing fillers.Id. More specifically, polypropylene with improved impact strength hasbeen produced by the addition of an amorphous material, a poorlycrystallized material or an elastomer, as EPDM, for example. Id.

High melt strength technology has been applied to production ofheterophasic propylene-ethylene copolymers to produce extrusion coatingresins with a unique combination of rigidity, heat resistance,toughness, pin-holing resistance and other properties. Beren at p. 97.The resin's strong strain hardening characteristic allows high-speedprocessing at low coating weights without draw resonance, Id.

The resins are high melt strength versions of heterophasicpropylene-ethylene copolymers, commonly known as medium-impactcopolymers and commonly abbreviated as HECOs. Id.

The distinguishing feature of HECO resins, from which they take theirname, is the presence of two distinct phases:

a continuous homopolymer base which provides rigidity and heatresistance.

a finely dispersed phase of ethylene-propylene rubber, a randomcopolymer of ethylene and propylene with ethylene predominating. Thisphase provides internal cushioning and elasticity, which improves impactstrength and tear resistance. Id.

Both phases are produced in situ in the reactor via a sequentialpolymerization process. Id. HECO resins are not produced by blending thematerials which form the two phases. Id.

HECO resins are well known in applications such as thermoforming, blowmolding, and injection molding, but have not normally been found inextrusion coating. Id.

The one method of producing a PP extrusion coating resin is to add aquantity, usually 12-20%, of branched LDPE to improve the melt strength.This allows coating speeds up to ˜200 m/min, but results in somecompromise of PP's properties, especially with respect to heatresistance. Id. More preferably, high performance polypropyleneextrusion coating can be used to produce high melt strength versions ofPP homopolymer and propylene-ethylene copolymers (both random andheterophasic). Id. For a more detailed discussion of the extensionalrheology of high melt strength polypropylene and its relationship toextrusion coating, please see “High Performance Polypropylene ExtrusionCoating Resins” by Phillips, McHugh and Bradley, Proceedings—1989 TAPPEPolymers Laminations and Coatings Conference, Orlando Fla., Sep. 5-8,1989, hereby incorporated herein by reference.

Two high melt strength HECO coating resins are exemplary:

-   -   A 20 MFR version offering the higher performance in terms of        impact strength and pin-holing resistance.    -   A 30 MFR version for less demanding applications.

Other less desirable materials include:

-   -   Homopolymer PP: A commercial 30 MFR resin offering high rigidity        and heat resistance. Produced using high melt strength        technology to coat at high speed without modification.    -   PP-LDPE Alloy: A commercial 15 MFR alloy with a linear PP        component and LDPE added for melt strength.    -   Randon Copolymer: A commercial 12 MFR resin used as a heat seal        layer in high temperature applications. Produced using high melt        strength technology to coat at high speed without modification.    -   HDPE: A commercial 7 MI resin.    -   LDPE: A commercial 8 MI resin. Id.

The standard physical properties of the HECO coating resins and other PPand PE coating are shown in Table 3, below:

TABLE 3 Standard resin physical properties PP-LDPE RANDOM PROPERTY HECOHOMO PP ALLOY COPO HDPE CDPE Tensile strength 26 37   25.4   29.5 20 12Flexural Modulus, MPa 1285  1900  — 1100  110  21 Rockwell Hardness, R81 100  83 89 — — Shore D — — — — 65 48 Notched Izod, J/mm 76 32 — 57 —— Heat Deflection Temp 93 121  75 86 68 46 @ 455 kPa ° C.

There is an important benefit of extrusion coating open-weave PP fabricswith HECO resins. Id at 98. A common example of such a fabric isopen-weave, or low-count, raffia. When coating with homopolymer or alloyresins, a void in the coating will tend to coincide with any sizable(>mm diameter) void in the fabric. It has been observed that this occursto a lesser extent when coating with HECO resins. Id, at 98.

The HECO material, like all the PP types, has much greater strength,rigidity, and heat resistance than any type of PE. It is also uniqueamong the PP types in the degree to which is maintains most ofhomopolymer polypropylene's heat resistance while gaining significantimpact strength. This is a manifestation of the material's dualcharacter of homopolymer continuous phase controlling some physicalproperties, while the propylene-ethylene rubber toughens it. Id. at 98.

The properties of heterophasic polypropylene copolymers are attractivefor extrusion coating in several respects, including:

-   -   excellent processability with high line speed and high draw        capabilities;    -   good pin-holing resistance, including excellent ability to        bridge voids in open-weave fabrics; and    -   a combination of heat resistance, rigidity and toughness unique        among polyolefin coating resins. Id, at 99.        Board Manufacturing

With reference to FIG. 5, a preferred method of continuouslymanufacturing cementitious boards is described.

While it is preferred that slightly-modified, conventional wallboard orcement board manufacturing equipment be employed for producing thecementitious boards 100 of this invention, cementitious boards 100 canbe manufactured in any number of ways, including molding, extrusion, andsemi-continuous processes employing rollers and segments of the fabricreinforcement 10 of this invention. As shown in FIG. 1, the fabricreinforcement 10 can be embedded in the cementitious core 101, such asto present a thin cementitious film 108 on the face of the board 100.The fabric reinforcement 10 can be embedded, or alternatively, beadhesively or mechanically bonded to the core 101 such as by the setcore 101, itself.

The cementitious board 100 includes a set cementitious core 101, made ofset gypsum or Portland cement, for example. The cementitious core 101preferably comprises a cementitious material, such as cement paste,mortar or concrete, and/or other types of materials such as gypsum andgeopolymers (inorganic resins). More preferably the inorganic matrixcomprises Portland cement having chopped fibers dispersed throughout thecement. Preferably the fibers are AR-glass fibers but may also include,for example, other types of glass fibers, aramids, polyolefins, carbon,graphite, polyester, PVA, polypropylene, natural fibers, cellulosicfibers, rayon, straw, paper and hybrids thereof. The inorganic matrixmay include other ingredients or additives such as fly ash, latex, slagand metakaolin, resins, such as acrylics, polyvinyl acetate, or thelike, ceramics, including silicon oxide, titanium oxide, and siliconnitrite, setting accelerators, water and/or fire resistant additives,such as silioxane, borax, fillers, setting retardants, dispersingagents, dyes and colorants, light stabilizers and heat stabilizers,shrinkage reducing admixtures, air entraining agents, settingaccelerators, foaming agents, or combinations thereof, for example. In apreferred embodiment, the inorganic matrix includes a resin that mayform an adhesive bond with a resinous coating applied to thealkali-resistant open fibrous layer. Preferably the cementitious core101 has good bonding with fabric reinforcement 10, but also may becomposite materials, including additional mats, or scrim of fabrics, forexample. The cementitious core 101 may contain curing agents or otheradditives such as coloring agents, light stabilizers and heatstabilizers, for example.

Examples of materials which have been reported as being effective forimproving the water-resistant properties of cementitious products eitheras a binder, finish or added coating, or performance additive 12 are thefollowing: poly(vinyl alcohol), with or without a minor amount ofpoly(vinyl acetate); metallic resinates; wax or asphalt or mixturesthereof; a mixture of wax and/or asphalt and also corn-flower andpotassium permanganate; water insoluble thermoplastic organic materialssuch as petroleum and natural asphalt, coal tar, and thermoplasticsynthetic resins such as poly(vinyl acetate), polyvinylchloride and acopolymer of vinyl acetate and vinyl chloride and acrylic resins; amixture of metal rosin soap, a water soluble alkaline earth metal salt,and residual fuel oil; a mixture of petroleum wax in the form of anemulsion and either residual fuel oil, pine tar or coal tar; a mixturecomprising residual fuel oil and rosin, aromatic isocyanates anddisocyanates; organohydrogenpolysiloxanes and other silicones, acrylics,and a wax-asphalt emulsion with or without such materials as potassiumsulfate, alkali and alkaline earth eliminates. Performance additives 12can be introduced directly into the cementitious slurry 28, in FIG. 5.The added coating can be applied to the fabric reinforcement 10 beforeand/or after joining to the cementitious core 101.

If gypsum is employed, the core may be formed by mixing water withpowdered anhydrous calcium sulfate or calcium sulfate hemidrate (Ca—SO₄½H₂O), also known as calcined gypsum, and thereafter allowing themixture to hydrate or set into calcium sulfate dihydrate (CaSO₄ 2H₂O), arelatively hard material. The cementitious core 101 of the supportmember will in general comprise at least about 85 wt. % set gypsum orcement.

The surface of the cementitious core 101 is faced with one or morelayers of the fabric reinforcement 10. The fabric reinforcement 10should be at least sufficiently porous to permit water in the aqueousslurry from which the core is made to evaporate therethrough, and may beporous enough to permit the slurry to pass through and form a continuousor discontinuous film. As described in the detail below, thecementitious board 100 in the present invention can be made efficientlyby forming an aqueous slurry which contains excess water and placingthereon the facing material. Aided by heating, excess water evaporatesthrough the preferred upper and lower glass fabric reinforcement 10 asthe slurry sets.

Continuous Manufacturing Method

An attractive feature of the present invention is that the cementitiousboard 100 can be made utilizing existing wallboard or cement boardmanufacturing lines, for example, as shown somewhat diagrammatically inFIG. 5. In conventional fashion, dry ingredients (not shown) from whichthe cementitious core 101 is formed are pre-mixed and then fed to amixer of the type commonly referred to as a pin mixer 30. Water andother liquid constituents (not shown) used in making the core aremetered into the pin mixer 30 where they are combined with the dryingredients to form an aqueous cementitious slurry 28. Foam is generallyadded to the slurry in the pin mixer 30 to control the density of theresulting cementitious core 101.

As is common practice in the manufacture of conventional paper-facedgypsum board, the two opposite edge portions of the bottom glass fabric22 are progressively flexed upwardly from the mean plane of the bottomglass fabric 22 and then turned inwardly at the margins so as to providecoverings for the edges of the resulting board 100, as shown in FIG. 1.

A sheet of top glass fabric 32 is fed from the top glass fabric roll 29onto the top of the cementitious slurry 28, thereby sandwiching theslurry between the two moving fabrics which form the facings of thecementitious core 101 which is formed from the cementitious slurry 28.The bottom and top glass fabrics 22 and 32, with the cementitious slurry28 sandwiched therebetween enter the nip between the upper and lowerforming or shaping rolls 34 and 36 and are thereafter received on aconveyor belt 38. Conventional wallboard edge guiding devices 40 shapeand maintain the edges of the composite until the slurry has setsufficiently to retain its shape. Water of convenience, or excess water,can be drained with the assistance of vacuum boxes 42 disposed below theconveyor belt 38. In due course, sequential lengths of the board are cutby a water knife 44. The cementitious board 100 is next moved alongfeeder rolls 46 to permit it to set. It is further processed by exposureto heat in a drying oven 48 which accelerates the drying of the board byincreasing the rate of evaporation of excess water. An additionalsprayer 49 can be provided to add further treatments, such as siliconeoil, additional coating, or fire retardants, to the board's exterior.The manufacturing techniques described in the “Background” section arealso acceptable.

The fabric reinforcement 10 and cementitious boards 100 of thisinvention are useful in all sorts of building construction applications.They are strong, having a screw strength of at least about 20 lbs., forgypsum cores of conventional densities and compositions. Some examplesinclude shaft wall assemblies for elevators and stairways, fire doorsand fire walls, roofing and siding substrates, with or withoutinsulation, and tile backer boards. Some of the most desirable anduseful applications for this invention are in EIF systems (also calledEIFS, for Exterior Insulation Finishing Systems), or as tile backerboards.

From the foregoing, it can be realized that this invention providesimproved coating techniques for fabrics and reinforcements, andspecifically enables a uniform coating to be applied to the warp andweft yarns of a knitted, braided, non-woven mesh-type, or woven fabricwithout VOC's and viscosity control constraints.

The present polyolefin soft compositions provide equal or betterperformance than plastisol coated laid scrim with similar drapabilityand lack of shape memory so as to be curved around the edge of a cementboard or gypsum wall board. The polyolefin compositions are much moreheat stable during manufacturing than PVC plastisol and produce farfewer VOCs. The polyolefin coatings do not contain any plasticizer inthe extrusion compositions and will always have the same viscosity andrheology at the same temperature. They also produce no void in thecoatings, especially when extruded over individual yarns so as tosubstantially uniformly coat the entire exterior surface area of theyarn. This enables them to be more corrosion resistant in alkalineenvironments than in earlier composed fabrics.

Although various embodiments have been illustrated, this is for thepurpose of describing, but not limiting, the invention. Variousmodifications, which will be apparent to one skilled in the art, arewithin the scope of this invention described in the attached claims.

What is claimed is:
 1. A method of making a fabric reinforcementcomprising: a) providing a plurality of glass yarns; b) extruding asubstantially uniform thickness of a softened polyolefin based polymericcomposition over said glass yarns to form coated glass yarns, thesoftened polyolefin based polymeric composition comprising: i) about70-80 wt % heterophasic polypropylene copolymer; ii) about 10-30 wt %polypropylene homopolymer; iii) about 0-5 wt % ethylene-olefincopolymer; iv) about 2-4 wt % maleic anhydride-g-polypropylene; v) about0-20 wt % inorganic filler; and vi) about 500-1500 ppm vinylidenefluoride-hexafluoroalkene copolymer; and c) forming a laid scrim withsaid coated yarns.
 2. The method of claim 1, wherein said laid scrim isdrapeable enough to form about a 0.5 inch radius without springing backto its original shape.
 3. The method of claim 1, further comprisingapplying a sizing to the glass yarns, the sizing being selected from thegroup consisting of: 1) an epoxy polymer, vinyl and amine couplingagents and a non-ionic surfactant; 2) an epoxy polymer, amine couplingagent and a non-ionic surfactant; 3) an epoxy polymer, methacrylic andepoxy coupling agents, and cationic and non-ionic surfactants; 4)anhydrous polymerized acrylate amine, methacrylic and epoxy couplingagents and a non-ionic surfactant; and 5) anhydrous polymerized epoxyamine, vinyl and amine coupling agents, and a non-ionic surfactant. 4.The method of claim 1 wherein said fabric reinforcement has a GurleyStiffness measurement of about 100-3000 mg and an ASTM D 638 (2% Secant)modulus of compression of about 1-100 MPa.
 5. The method of claim 1wherein said inorganic filler comprises talc.
 6. The method of claim 1wherein said ethylene-olefin comprises an ethylene-α olefin.
 7. Themethod of claim 1 wherein said fabric reinforcement has a GurleyStiffness measurement of about 500-2,500 mg and an ASTM D 638 (2%Secant) modulus of compression of about 5-35 MPa.
 8. The method of claim1, wherein, during step (a), two or more strands twisted together with afirst twist are plied with a second twist in order to form a balancedyarn.
 9. The method of claim 1, wherein extruding comprises extrudingthe softened polyolefin based polymeric composition over individual onesof said glass yarns.
 10. The method of claim 1, wherein the glass yarnscomprise zero twist yarns.